sync: Move all the js_* files into a js/ subdirectory.

chrome/browser/sync/README.js

 Overview of chrome://sync-internals
 -----------------------------------
 
 This note explains how chrome://sync-internals (also known as
 about:sync) interacts with the sync service/backend.
 
 Basically, chrome://sync-internals sends messages to the sync backend
 and the sync backend sends the reply asynchronously.  The sync backend
 also asynchronously raises events which chrome://sync-internals listen
 to.
 
 A message and its reply has a name and a list of arguments, which is
 basically a wrapper around an immutable ListValue.
 
 An event has a name and a details object, which is represented by a
 JsEventDetails (js_event_details.h) object, which is basically a
 wrapper around an immutable DictionaryValue.
 
-TODO(akalin): Move all the js_* files into a js/ subdirectory.
-
 Message/event flow
 ------------------
 
 chrome://sync-internals is represented by SyncInternalsUI
 (chrome/browser/ui/webui/sync_internals_ui.h).  SyncInternalsUI
 interacts with the sync service via a JsController (js_controller.h)
 object, which has a ProcessJsMessage() method that just delegates to
 an underlying JsBackend instance (js_backend.h).  The SyncInternalsUI
 object also registers itself (as a JsEventHandler
 [js_event_handler.h]) to the JsController object, and any events
@@ skipping 10 matching lines @@
 
 - SyncInternalsUI (implements JsEventHandler, JsReplyHandler)
 - SyncJsController (implements JsController, JsEventHandler)
 
 The following objects live on the sync thread:
 
 - SyncManager::SyncInternal (implements JsBackend)
 
 Of course, none of these objects need to know where the other objects
 live, since they interact via WeakHandles.